In a conventional image forming apparatus, an upper cover rotatable about one side of an upper portion of the apparatus is provided and an LED (Light Emitting Diode) head assembly having an LED head is arranged on an inner surface of the upper cover, and, inside the apparatus, a photosensitive unit formed by integrating a photosensitive drum, a charging part, a development part, and a toner cartridge is detachably arranged, and, in a state in which the upper cover is closed, a light emitting surface of the LED head is arranged at a position where the photosensitive drum can be exposed. Further, in a color printer as an image forming apparatus, in order to form an image using developers of a plurality of colors, a photosensitive unit and an LED head for each of the developers of the respective colors are arranged in a carrying direction of a recording medium in the apparatus main body or on the upper cover (for example, see Patent Document 1).